1. Field of the Invention
This invention relates to grooved substrates for positioning and retaining optical fibers to be used in optical communications, and more particularly to the grooved substrates for use in multifiber optical connectors which can realize coupling of the connectors by using guide pins or the grooved substrates for aligning the multiple optical fibers, which substrate is capable of positioning and retaining the optical fibers therein. This invention also relates to methods for the production thereof.
2. Description of the Prior Art
As an optical connector to be used for connecting the optical fibers to each other, heretofore, the fitting type optical connector as shown in FIGS. 1 and 2, for example, is known in the art. The multifiber optical connector 10a (in the example shown in the drawings, four-fiber optical connector) is basically composed of a V-grooved substrate 11 and a retaining substrate 14 fixed to the V-grooved substrate 11 through the medium of an adhesive. The V-grooved substrate 11 is provided with a plurality of V-grooves 12 for optical fibers formed therein parallel to each other, each groove having a cross-sectional contour of the letter V, and V-grooves 13 for guide pins formed on the opposite side of the V-grooves 12. By joining the retaining substrate 14 to the V-grooved substrate 11, the holes for optical fibers and those for guide pins are respectively formed by the V-grooves 12 for optical fibers and the V-grooves 13 for guide pins in the joining area thereof. The multifiber optical connector 10a is prepared by inserting and adhering the optical fibers 16 into the holes for optical fibers and polishing the end face of the assembled connector. Another multifiber optical connector 10b is similarly provided with a plurality of holes for optical fibers into which the optical fibers 16 are inserted and adhered, but has guide pins 15 projected at the positions aligned with the V-grooves 13 for guide pins mentioned above. The mutual coupling of the optical connectors 10a, 10b is performed by inserting the guide pins 15 into the holes for guide pins mentioned above. The reference numeral 17 denotes a fiber tape.
The V-grooved substrate for aligning multiple optical fibers is also used in a mechanical splice for abutting, the optical fibers against each other and joining them by fusion thereof or through the medium of an agent for adjusting the refractive index, to align and retain the optical fibers therein. FIGS. 3 and 4 illustrate an example of the four-fiber mechanical splice. The mechanical splice 20 is composed of a V-grooved substrate 21 having V-grooves 22 formed therein for positioning the optical fibers 16, a retaining substrate 25, and a clamp spring 28 of the snap-in fitting type capable of exerting the holding power to clamp them. The V-grooved substrate 1 is provided with guide grooves 24 respectively formed at opposite ends of the parallel V-grooves 22 and wedge guide grooves 23 of a prescribed number (four, in the example shown in the drawing) at one longitudinal edge. Similarly, the retaining substrate 25 is provided with wedge guide grooves 26 formed therein at the position aligned with the wedge guide grooves 23 mentioned above. Each wedge insertion hole 27 is formed by a pair of upper and lower wedge guide grooves 23 and 26. The attachment of the optical fibers 16 to the mechanical splice 20 is performed by inserting wedges 29 into the wedge insertion holes 27 mentioned above to form a gap between the substrates 21 and 25, inserting the optical fibers 16 into the gap from opposite ends so as to abut the ends of the optical fibers against each other, and pulling the wedges 29 out of the holes 27 thereby allowing the upper and lower substrates 21 and 25 to be clamped with the clamp spring 28 and establishing the connection of the optical fibers.
As the materials for the V-grooved substrates, heretofore, a wafer of silicon single crystal as disclosed in published Japanese Patent Application, KOKAI (Early Publication) No. (hereinafter referred to briefly as xe2x80x9cJP-A-xe2x80x9d) 6-82656 and JP-A-5-134146, alumina, or a glass filler-containing epoxy :resin as disclosed in JP-A7-181338 is used. The V-grooves are formed by the anisotropic etching of silicon when the wafer of silicon single crystal is used as the substrate material or by the grinding process when alumina is used. In the case of an epoxy resin, the V-grooved substrate is manufactured by the injection molding.
In the manufacture of the V-grooved substrates for multifiber optical connectors, it is very important to minimize the clearance between the guide pin and the guide pin hole as possible, without mentioning that the positioning of the optical fiber holes to the guide pin holes and the mutual distance between the optical fiber holes should be adjusted in the submicron order.
When a wafer of silicon single crystal is used as a substrate material, the V-grooves are formed by the anisotropic etching of silicon as mentioned above. However, this processing is expensive. Further, the guide pin holes entail such problems as wear and micro-deformation thereof when the guide pins are frequently attached to and detached from the guide pin holes of the above substrate, which increases the clearance between the guide pin and the guide pin hole and eventually results in the deviation from the mutual alignment of the optical fibers. As a result, it will be difficult to connect the optical fibers stably with a low connector insertion loss.
When the substrate material is alumina, it takes a longer time for forming V-grooves. In addition thereto, since it needs the grinding process with high processing cost, the V-grooved substrate obtained will be inevitably expensive.
On the other hand, when the V-grooved substrate is manufactured from an epoxy resin, it can be produced by the injection molding at a low cost. It poses, however, a serious problem of the increase in the clearance between the guide pin and the guide pin hole with the repeated attachment and detachment of the guide pin to and from the hole, as in the case of the substrate made from the wafer of silicon single crystal.
As described above, heretofore, it is not possible to manufacture the grooved substrate that allows the multifiber optical connector to stably maintain the low connector insertion loss (no increase in the clearance between the guide pin and the guide pin hole) at a low cost from the conventional materials such as the wafer of silicon single crystal, alumina, and epoxy resins.
The grooved substrate for aligning multiple optical fibers is also required to possess the mechanical strength, wear resistance, and other properties because wedges are used to release the clamping action.
It is, therefore, an object of the present invention to provide an inexpensive grooved substrate which possesses a sufficient strength, incurs only sparingly such problems mentioned above as causing wear and micro-deformation by the repeated attachment and detachment of the guide pins or the wedges and allows an optical connector prepared by using this grooved substrate to maintain the stable low connector insertion loss.
A further object of the present invention is to provide a method which, owing to the combination of a technique based on the conventional metal mold casting process or molding process with the quality of an amorphous alloy exhibiting a glass transition region, allows a grooved substrate satisfying a predetermined shape, dimensional accuracy, and surface quality to be mass-produced with high efficiency by a simple process and, therefore, enables to omit or diminish markedly such machining steps as grinding and consequently provide an inexpensive grooved substrate excelling in durability, strength, resistance to impact, resistance to wear, elasticity, etc. expected of the grooved substrate.
To accomplish the object mentioned above, the first aspect of the present invention provides a grooved substrate for positioning and retaining optical fibers, particularly a grooved substrate for use in a multifiber optical connector which realizes coupling of the connectors by using guide pins or a grooved substrate for aligning and retaining the optical fibers, which is characterized by being manufactured from an amorphous alloy instead of a wafer of silicon single crystal, alumina, or an epoxy resin which has been heretofore used. The groove may have the cross-sectional contour of substantially the Letter V, as in the conventional V-grooved substrate, or substantially the letter U.
The first embodiment of the grooved substrate according to the present invention is characterized by being manufactured from an amorphous alloy possessing at least a glass transition region, preferably a glass transition region of a temperature width of not less than 30 K.
In a preferred embodiment, the grooved substrate is characterized by being formed of a substantially amorphous alloy having a composition represented by either one of the following general formulas (1) to (6) and containing an amorphous phase in a volumetric ratio of at least 50%:
M1aM2bLncM3dM4eM5fxe2x80x83xe2x80x83(1)
wherein M1 represents either or both of the two elements, Zr and Hf; M2 represents at least one element selected from the group consisting of Ni, Cu, Fe, Co, Mn, Nb, Ti, V, Cr, Zn, Al, and Ga; Ln represents at least one element selected from the group consisting of Y, La, Ce, Nd, Sm, Gd, Tb, Dy, Ho, Yb, and Mm (mish metal: aggregate of rare earth elements); M3 represents at least one element selected from the group consisting of Be, B, C, N, and O; M4 represents at least one element selected from the group consisting of Ta, W, and Mo; M5 represents at least one element selected from the group consisting of Au, Pt, Pd, and Ag; and a, b, c, d, e, and f represent such atomic percentages as respectively satisfy 25xe2x89xa6axe2x89xa685,15xe2x89xa6bxe2x89xa675,0xe2x89xa6cxe2x89xa630,0xe2x89xa6dxe2x89xa630,0xe2x89xa6exe2x89xa615, and 0xe2x89xa6fxe2x89xa615.
xe2x80x83Al100xe2x88x92gxe2x88x92hxe2x88x92iLngM6hM3ixe2x80x83xe2x80x83(2)
wherein Ln represents at least one element selected from the group consisting of Y, La, Ce, Nd, Sm, Gd, Tb, Dy, Ho, Yb, and Mm; M6 represents at least one element selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zr, Nb, Mo, Hf, Ta, and W; M3 represents at least one element selected from the group consisting of Be, B, C, N, and O; and g, h, and i represent such atomic percentages as respectively satisfy 30xe2x89xa6gxe2x89xa690,0xe2x89xa6hxe2x89xa655, and 0xe2x89xa6ixe2x89xa610.
Mg100xe2x88x92pM7pxe2x80x83xe2x80x83(3)
wherein M7 represents at least one element selected from the group consisting of Cu, Ni, Sn, and Zn; and p represents an atomic percentage falling in the range of 5xe2x89xa6pxe2x89xa660.
Mg100xe2x88x92qxe2x88x92rM7gM8rxe2x80x83xe2x80x83(4)
wherein M7 represents at least one element selected from the group consisting of Cu, Ni, Sn, and Zn; M8 represents at least one element selected from the group consisting of Al, Si, and Ca; and q and r represent such atomic percentages as respectively satisfy 1xe2x89xa6qxe2x89xa635 and 1xe2x89xa6rxe2x89xa625.
Mg100xe2x88x92qxe2x88x92sM7qM9sxe2x80x83xe2x80x83(5)
wherein M7 represents at least one element selected from the group consisting of Cu, Ni, Sn, and Zn; M9 represents at least one element selected from the group consisting of Y, La, Ce, Nd, Sm, and Mm; and q and s represent such atomic percentages as respectively satisfy 1xe2x89xa6qxe2x89xa635 and 3xe2x89xa6sxe2x89xa625.
Mg100xe2x88x92qxe2x88x92rxe2x88x92sM7qM8rM9sxe2x80x83xe2x80x83(6)
wherein M7 represents at least one element selected from the group consisting of Cu, Ni, Sn, and Zn; M8 represents at least one element selected from the group consisting of Al, Si, and Ca; M9 represents at least one element selected from the group consisting of Y, La, Ce, Nd, Sm, and Mm; and q, r, and s represent such atomic percentages as respectively satisfy 1xe2x89xa6qxe2x89xa635,1xe2x89xa6rxe2x89xa625, and 3xe2x89xa6sxe2x89xa625.
The second aspect of the present invention provides methods for the production of the grooved substrates as mentioned above.
One mode of the methods is characterized by comprising the steps of melting an alloying material capable of producing an amorphous alloy in a melting vessel having an upper open end, forcibly transferring the resultant molten alloy into a forced cooling casting mold disposed above the vessel and provided with at least one molding cavity, and rapidly solidifying the molten alloy in the forced cooling casting mold to confer amorphousness on the alloy thereby obtaining the product made of an alloy containing an amorphous phase.
In a preferred embodiment of this method, the melting vessel is furnished therein with a molten metal transferring member adapted to forcibly transfer the molten alloy upward, the forced cooling casting mold is provided with at least two identically shaped molding cavities and runners severally communicating with the cavities, and the runners are disposed on an extended line of a transfer line for the molten metal transferring member.
Another method is characterized by comprising the steps of providing a vessel for melting and retaining an alloying material capable of producing an amorphous alloy possessing a glass transition region, providing a metal mold provided with at least one cavity of the shape of the product aimed at, coupling a hole formed in, for example, the lower or upper part of the vessel with a sprue of the metal mold, for example by disposing the metal mold beneath or on the vessel, applying pressure on a melt of the alloy in the vessel thereby enabling a prescribed amount of the melt to pass through the hole of the vessel and fill the cavity of the metal mold, and solidifying the melt in the metal mold at a cooling rate of not less than 10 K(Kelvin scale)/sec. thereby giving rise to the product of an alloy containing an amorphous phase.
In any of the methods described above, as the alloying material mentioned above, a material capable of producing a substantially amorphous alloy having a composition represented by either one of the aforementioned general formulas (1) to (6) and containing an amorphous phase in a volumetric ratio of at least 50% is advantageously used.
Still another method of the present invention is characterized by comprising the steps of heating a material formed of a substantially amorphous alloy having a composition represented by either one of the general formulas (1) to (6) mentioned above and containing an amorphous phase in a volumetric ratio of at least 50% until the temperature of a supercooled liquid region, inserting the resultant hot amorphous material into a container held at the same temperature, coupling with the container a metal mold provided with a cavity of the shape of the product aimed at, and forcing a prescribed amount of the alloy in the state of a supercooled liquid into the metal mold by virtue of the viscous flow thereof.